Title

Author

Degree Type

Dissertation

Date of Award

1987

Degree Name

Doctor of Philosophy

Department

Agronomy

Abstract

Evaluation of 120 unselected S(,1) lines from each of the BS11CO and BS11(FR)C6 maize (Zea mays L.) populations was conducted to investigate changes in means, genotypic variances and phenotypic correlations that have occurred after six cycles of reciprocal full-sib selection. Mechanically harvestable grain yield, grain moisture, stalk lodging, root lodging and dropped ears were measured at Kanawha and Martinsburg in 1981 and 1982. Twenty-nine agronomic traits were measured at Ames in 1981 and 1982. Variance components, heritabilities, means, and phenotypic and genotypic correlations among traits were estimated for combined analyses;Significant decreases in genetic variability, associated with reciprocal full-sib selection, were detected for 13 traits. Eleven traits were significantly changed through selection. The changes in means and variances of traits were attributed to both selection and inbreeding. Changes in genotype x environment interaction variances and their effects on heritability were discussed. Changes in phenotypic correlations between traits and their impact on continued selection were discussed;Artificial inoculation of stalk rot organisms failed to cause significant reductions in grain yield components although it significantly increased stalk lodging. Incorporation of artificial inoculation of stalk rot organisms and subsequent rind puncture and stalk lodging evaluation of S(,1) families in breeding programs were recommended for BS11 because of the favorable associations between these measures of stalk quality and reduced stalk lodging. Root pulling of S(,1) families was also recommended because of normal distribution of the data, lack of consistent expression in root lodging, and favorable associations between root pull scores and reduced root lodging and improved stalks.